The present technology generally relates to a positive electrode active material used for a secondary battery, a positive electrode and a secondary battery that use the positive electrode active material, and a battery pack, an electric vehicle, an electric power storage system, an electric power tool, and an electronic apparatus that use the secondary battery.
Various electronic apparatuses such as a mobile phone and a personal digital assistant (PDA) have been widely used, and it has been demanded to reduce the sizes and weights of the electronic apparatuses and to achieve their long life. Accordingly, as an electric power source for the electronic apparatuses, a battery, in particular, a small and light-weight secondary battery capable of providing high energy density has been developed.
It has been considered to apply a secondary battery not only to the foregoing electronic apparatuses, but also to other applications. Examples of other applications include a battery pack detachably mounted on electronic apparatuses or the like, an electric vehicle such as an electric automobile, an electric power storage system such as a home electric power server, and an electric power tool such as an electric drill.
The secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution, and the positive electrode contains a positive electrode active material. Since the configuration of the positive electrode active material exerts a large influence on battery characteristics, various studies have been made on the configuration of the positive electrode active material.
Specifically, the concentration distribution of main constituent elements contained in a positive electrode active material can be optimized in order to improve cycle characteristics and the like.